Closure unit

ABSTRACT

A vertically closing closure unit for an injection molding machine includes a moveable mold mounting plate, and at least one frame bar for guiding the moveable mold mounting plate. A restraint device locks the moveable mold mounting plate to the at least one frame bar.

The present invention concerns a vertically closing closure unit for an injection molding machine having the features of the classifying portion of claim 1.

For safety reasons vertically closing closure units of injection molding machines must have restraint devices which prevent a moveable mold mounting plate from dropping down if a defect for example in the rapid-action mechanism occurs. In the state of the art they are mounted to the rapid-action devices. In particular in the case of hydraulic rapid-action devices the restraint devices are in the form of clamping devices which if required act directly at the rapid-action cylinders. A basic problem with such restraint devices is that, in the event of structural failure of certain components of the rapid-action device or the restraint devices—for example fracture of fixing pins—the moveable mold mounting plate nonetheless drops down. This means that such components have to be over-sized to afford a certain safety cushion. Naturally that increases the production cost for such closure units.

The object of the invention is to provide a vertically closing closure unit for an injection molding machine, which is equipped with a less expensive and more reliable restraint device.

That object is attained with a vertically closing closure unit having the features of claim 1.

That is achieved by the provision of a restraint device for locking the moveable mold mounting plate to the at least one frame bar. Because the frame bars in any case are of a sufficiently strong structure to hold the moveable mold mounting plate, that gives a reduction in the components which have to be constructed with a safety margin. That leads to increased security and safety and reduced production cost.

Further advantageous embodiments of the invention are recited in the appendant claims.

For optimum space utilization the restraint device can be fixed to the moveable mold mounting plate.

It is preferably provided that locking is effected by positively locking connection of the restraint device to at least one support surface on the at least one frame bar. Force-locking restraint devices like for example redundant clamping devices are on the one hand costly and on the other hand have to be regularly checked—generally once a month. That is naturally detrimental to productivity. Such disadvantages are avoided by a positively locking locking action.

A particularly preferred embodiment is one in which the restraint device is formed by a locking mechanism which serves to lock the moveable mold mounting plate in the event of a closing pressure build-up. Due to the doubled use of the locking mechanism that represents a particularly inexpensive structure. That double use is particularly simple to implement if the locking mechanism is in the form of at least one—preferably divided—locking nut.

A particularly preferred embodiment is one in which in the locked condition no force working towards unlocking of the restraint device acts when the locking drive is switched off as that also ensures safety in the event of failure of the locking drive.

The positively locking locking action can be particularly easily implemented if the at least one support surface is formed by a top side of the at least one frame bar.

It can however also be provided that the at least one frame bar has an outside profile and the at least one support surface is formed by at least one flank of the outside profile. That can provide for increased safety in particular in the case of large machines.

It can be advantageous if the at least one frame bar is of such a configuration that the restraint device is lockable to the at least one frame bar in any position of the moveable mold mounting plate, in particular that the outside profile extends so far over a length of the at least one frame bar that the restraint device is lockable to the at least one frame bar in any position of the moveable mold mounting plate. That makes the work of the operator easier for example when fitting a new injection molding tool.

The locking means according to the invention can be provided for various positions of the moveable mold mounting plate, in particular for an upper maximum position of the moveable mold mounting plate. In that respect the upper maximum position can be defined by the maximum height of the mold mounting plate that can be reached by means of the rapid-action device.

The kind of rapid-action device or locking drive is not essential to the invention. For example they can be hydraulic, electric, magnetic or pneumatic.

Protection is also sought for an injection molding machine having a closure unit according to the invention.

Protection is further sought for a method of upwardly restraining a moveable mold mounting plate of a vertically closing closure unit according to the invention to guarantee safe access to the region of the closure unit for operating personnel. That can be achieved by the restraint device according to the invention being locked, a lifting force exerted by the rapid-action device being reduced and by a signal which signals access clearance to the operating personnel being produced when the lifting force falls below a force limit value.

In that respect it can be provided that the moveable mold mounting plate is locked in the upper maximum position or in any intermediate position.

It can further be provided that, to carry out the method, only one button on an operating unit has to be actuated and the various method steps are then performed by the machine control. In that respect however it can also be provided that a button must remain actuated for implementation of the method by the machine control, that is to say the operator must remain with the finger on the button.

To make as much space as possible available for for example the operating personnel it can be provided that the moveable mold mounting plate is moved into an upper maximum position before locking of the restraint device.

To implement a purely mechanical restraint device in machines with moveable frame bars it can be provided that before the signal is produced the at least one frame bar is moved into a lowermost position of a calibrated stroke movement.

In regard to easy recognizability it can be provided that this signal is produced optically, that preferably occurring at access doors to the closure region.

Further advantages and details of the invention will be apparent from the Figures and the related specific description. In the Figures:

FIG. 1 a shows a diagrammatic sectional view through a vertical closure unit according to the invention, which is locked in the upper maximum position,

FIG. 1 b shows a detail view of the positively locking locking situation of FIG. 1 a,

FIG. 2 shows a diagrammatic sectional view of a vertical closure unit according to the invention which is locked in a central position,

FIG. 3 shows a diagrammatic sectional view of a vertical closure unit according to the invention which is locked in an upper maximum position, and

FIG. 4 shows an injection molding machine having a vertical closure unit according to the invention.

In the closure unit diagrammatically shown in FIG. 1 a it is possible to see firstly the fixed mold mounting plate 12, the moveable mold mounting plate 2, the frame bars 3, the rapid-action devices 9, the pressure cushions 13 and the upward restraint device 4. In this case the restraint device 4 comprises a respective divided locking nut 6 for each frame bar and a locking drive 7 for two respective locking nuts 6, wherein the locking drive 7 is here hydraulic. The locking nuts 6 are fixed to the moveable mold mounting plate 2.

In this case the at least support surface 5 is formed by the top side of the frame bars 3.

This can better be seen from the detail view in FIG. 1 b showing a flank of an inside profile of a locking nut 6 resting on the top side of a frame bar 3.

In this first embodiment the rapid-action device 9 is in the upper maximum position.

As shown in FIG. 2 in this embodiment the moveable mold mounting plate 2 can also be locked in a central position as the frame bars 3 have outside profiles 8.

Two respective halves of divided locking nuts 6 are coupled in motionally connected relationship by way of linkages.

In this case the at least one support surface 5 is formed by lower flanks of the outside profile 8 of the frame bars 3. All other references correspond to those in FIG. 1 and are not further referred to hereinafter.

FIG. 3 shows a further embodiment in which restraint is also implemented in the upper maximum position (as shown) by engagement of the locking nuts 6 into an outside profile 8 of the frame bars 3. This embodiment represents a particularly secure but also somewhat more expensive structure as the frame bars must be longer than in the previous embodiments.

FIG. 4 shows an injection molding machine 1 having a vertical closure unit 10 according to the invention and an injection unit 11.

The present invention is not limited to the embodiments illustrated here. For example the restraint device can also be embodied by a separate locking device—for example by a locking member in bolt form, which rests on the top side of the frame bars or engages through a through opening in the frame bars. All drives in the present embodiments are admittedly hydraulic. That however is irrelevant for the invention can equally well be used for electric drives or any other kinds of drive. 

1. A vertically closing closure unit for an injection molding machine comprising a moveable mold mounting plate, and at least one frame bar for guiding the moveable mold mounting plate, characterised in that there is provided a restraint device for locking the moveable mold mounting plate to the at least one frame bar.
 2. A closure unit as set forth in claim 1 characterised in that the restraint device is connected to the moveable mold mounting plate.
 3. A closure unit as set forth in claim 1 characterised in that locking is effected by positively locking connection of the restraint device to an at least one support surface on the at least one frame bar.
 4. A closure unit as set forth in claim 1 in that the restraint device is formed by a locking mechanism which serves to lock the moveable mold mounting plate in the event of a closing pressure build-up.
 5. A closure unit as set forth in claim 4 characterised in that the locking mechanism is in the form of at least one—preferably divided—locking nut.
 6. A closure unit as set forth in claim 1 characterised in that there is provided a locking drive by which the restraint device is lockable.
 7. A closure unit as set forth in claim 6 characterised in that in the locked condition no force working towards unlocking of the restraint device acts when the locking drive is switched off.
 8. A closure unit as set forth in claim 1 characterised in that the at least one support surface is formed by a top side of the at least one frame bar.
 9. A closure unit as set forth in claim 1 wherein the at least one frame bar has an outside profile, characterised in that the at least one support surface is formed by at least one flank of the outside profile.
 10. A closure unit as set forth in claim 1 characterised in that the at least one frame bar is of such a configuration that the restraint device is lockable to the at least one frame bar in any position of the moveable mold mounting plate, in particular that the outside profile extends so far over a length of the at least one frame bar that the restraint device is lockable to the at least one frame bar in any position of the moveable mold mounting plate.
 11. A closure unit as set forth in claim 1 wherein there is provided a rapid-action device for moving the moveable mold mounting plate into an upper maximum position, characterised in that the restraint device is lockable when the moveable mold mounting plate is in the upper maximum position.
 12. A closure unit as set forth in claim 1 characterised in that the rapid-action device and/or the locking drive is hydraulic, electric, magnetic or pneumatic.
 13. An injection molding machine comprising a closure unit as set forth in claim
 1. 14. A method of upwardly restraining a moveable mold mounting plate of a vertically closing closure unit as set forth in claim 1 characterised in that the restraint device is locked, a lifting force exerted by the rapid-action device is reduced, and when the lifting force falls below a force limit value a signal which signals access clearance to the operating personnel is produced.
 15. A method as set forth in claim 14 characterised in that the moveable mold mounting plate is moved into an upper maximum position before locking of the restraint device.
 16. A method as set forth in claim 14 for a closure unit whose at least one frame bar is moveable characterised in that before the signal is produced the at least one frame bar is moved into a lowermost position of a calibrated stroke movement.
 17. A method as set forth in claim 14 characterised in that the signal is produced optically, wherein that is preferably effected at access doors to the closure region. 